The present invention relates generally to optical devices and optical systems, and more particularly to a device for modulating a light beam intensity and a projector/exposure system using such a device.
Devices which modulate an aspect of a light beam, e.g. an amplitude or phase of the light, find a number of applications. In optical modulation applications, phase modulation is often more important than amplitude modulation. Furthermore, phase modulation devices can often perform amplitude modulation, thereby providing application flexibility. It is desired to provide a light modulation device that is fast, reliable, durable, efficient, and can be used in simple as well as complex applications.
A technical advance is provided by a new and unique light modulation element, device, and system. In one embodiment, the light modulation element includes three electrodes, a flexible member, and a mirror. The flexible member is connected between the three electrodes so that the first and second electrodes are on one side and the third electrode is on the opposite side of the flexible member. The mirror is attached to the flexible member so that it can move therewith. The flexible member moves responsive to an external force provided by one or more of the three electrodes so that the mirror is positioned in a predetermined position responsive to the state of the flexible member.
In another embodiment, the light modulation element includes a substrate with first and second electrodes positioned adjacent to the substrate. One or more support members are connected to the substrate for supporting a flexible member extending over and above the first and second electrodes. In one embodiment, the second electrode is near a center portion of the flexible member. The light modulation element also includes a third electrode positioned above the flexible member and a mirror connected to and extending above the flexible member. As a result, the flexible member can be moved by changing electrostatic forces applied by one or more of the electrodes, and the mirror is moved with the flexible member.
In one embodiment, the light modulation device has a substrate and an array of light modulation elements. Each light modulation element includes first and second electrodes positioned proximate to the substrate and a flexible member extending over and above the first and second electrodes. A third electrode is positioned above the flexible member, and a mirror is connected to and extends above the flexible member. The flexible member can move between a first and second state responsive to forces affected by the electrodes so that a distance of the mirror from the substrate is controlled by the state of the flexible member.
In one embodiment, the system is a projection system such as can be used for lithography. The system includes a light source for producing a light of wavelength xcex, a beamsplitter having a reflective surface, a micro-mirror device, and a reflecting device. The beamsplitter receives the light from the light source and directs a first portion of the light to the micro-mirror device and a second portion of the light to the reflecting device. The micro-mirror device includes a plurality of individual mirrors manipulatable between a first and second state. In some embodiments, the micro-mirror device (when the mirrors are in the first state) and the reflective device are positioned at a common distance from the reflective surface. The micro-mirror device, beamsplitter, and reflecting device are also positioned so that the first and second portions of light will meet. A distance traveled by the first portion of light is controllable by the different states of each mirror so that when the first and second portions of light meet, an aspect (e.g., phase or amplitude) of the light can be modulated using optical interference.